As polymeric materials have replaced traditional materials such as metal and glass as a more cost-effective, lightweight, and design-friendly alternative, certain desirable materials properties have been sacrificed in some applications. Gas permeation through the material is one of these properties. While metal and glass are completely non-permeable to gases, polymeric materials almost universally allow some level of gas permeation through the material. This property of polymers initially proved problematic in industries such as food packaging, where shelf-life is a function of the rate of oxygen permeability through the packaging material. Polymeric barrier materials have been developed to address this problem, but even the best polymeric gas barriers only slow the rate of gas permeation and cannot completely prevent it.
Polymeric materials have proven to be particularly problematic in applications where limiting the permeation of very small gas molecules, such as helium, is desired. Further, even structures made from gas impermeable materials are susceptible to helium leakage at joints or seams if such joints include polymeric materials such as adhesives.